Update: Influenza Activity --
New York and United States, 1994-95 Season

Influenza activity in the United States during the current
influenza season began in the Northeast, and during late January,
spread to other regions of the country. This report describes
influenza outbreaks in nursing homes in New York and summarizes
national influenza surveillance data from October 2, 1994, through
February 11, 1995.
New York

The first influenza outbreak reported to CDC during the 1994-
95 season occurred in a 300-bed skilled-nursing facility in Long
Island, New York. On November 30, 1994, eight residents on one
20-bed corridor developed influenza-like illness (ILI) (i.e., fever
greater than or equal to 100 F {greater than or equal to 38 C} and
cough). On December 1, nasopharyngeal swab specimens from these
eight residents were submitted for rapid antigen testing; within 5
hours after transport to the laboratory, influenza type A was
detected by enzyme immunoassay in six specimens. On the evening of
December 1, 293 of the 299 residents in the facility each received
100 mg of amantadine hydrochloride as treatment for the eight ill
residents and as prophylaxis against influenza A infection for the
other 285 residents. Most (285 {95%}) residents had received
influenza vaccine before the outbreak. On December 2, as part of
the nursing home's contingency plan for influenza outbreaks,
amantadine dosages were modified for individual residents based on
estimated creatinine clearance (1,2), and prophylaxis was continued
for 14 days. Other outbreak-control measures included confining ill
residents to their rooms for at least 72 hours after the initiation
of amantadine treatment and prophylaxis, confining all residents to
their individual units, suspending group activities, and minimizing
the assignment of nursing staff to multiple units. The amantadine
dosage subsequently was discontinued for five residents and reduced
for 13 residents because of side effects (primarily confusion and
agitation); for most patients, side effects resolved within 48
hours of dosage adjustment.

During the first 48 hours of amantadine prophylaxis and
treatment, six additional residents developed ILI. Of the 14
residents who developed outbreak-associated ILI, five subsequently
developed clinical pneumonia. During the 2-week period of
amantadine prophylaxis, sporadic cases of febrile respiratory
illness occurred in other units of the facility; however, there was
no clustering of cases.

Tissue culture of all eight nasopharyngeal specimens yielded
influenza type A(H3N2). These isolates were further characterized
at CDC; all were antigenically similar to the A/Shangdong/09/93
strain included in the 1994-95 influenza vaccine.

Influenza surveillance in New York state indicated increasing
activity beginning in late November 1994. From December 1, 1994,
through February 11, 1995, outbreaks associated with influenza type
A(H3N2) in 46 other nursing homes were reported to the New York
State Department of Health (NYSDOH); of these, 16 were reported
from nursing homes in Long Island. For all 16 facilities, influenza
type A infection was documented by rapid antigen detection; in 13
facilities, amantadine was administered as an outbreak-control
measure. Outbreaks in five other nursing homes were caused by
influenza type B and, in two nursing homes, by influenza types A
and B. Based on findings of virologic surveillance in New York,
influenza has occurred in persons in all age groups during the
1994-95 season. Of the 385 influenza virus isolates reported by
laboratories in New York this season, 332 (86%) have been type A.
United States

From November 27, 1994, through January 21, 1995, most
influenza activity was reported from the Northeast (3). However,
during January 22-February 11, regional or widespread activity was
reported from states in every region.

Through February 11, World Health Organization collaborating
laboratories reported 1282 influenza virus isolates; of these, 923
(72%) isolates have been type A and 359 (28%) have been type B. Of
the influenza A isolates that have been subtyped, all have been
type A(H3N2).

The proportion of deaths attributable to pneumonia and
influenza reported from 121 U.S. cities slightly exceeded the
epidemic threshold during six of the 19 weeks from October 2, 1994,
through February 11, 1995, but has not exceeded the threshold for
any 2 consecutive weeks.
Reported by: IH Gomolin, MD, Gurwin Jewish Geriatric Center,
Commack, New York; HB Leib, MS, RJ Gallo, S Kondracki, G Brady, G
Birkhead, MD, DL Morse, MD, State Epidemiologist, New York State
Dept of Health. Participating state and territorial epidemiologists
and state public health laboratory directors. World Health
Organization collaborating laboratories. Sentinel Physicians
Influenza Surveillance System of the American Academy of Family
Physicians. WHO Collaborating Center for Surveillance,
Epidemiology, and Control of Influenza, Div of Viral and
Rickettsial Diseases, National Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: Influenza vaccination is 70%-90% effective in
preventing ILI in young, healthy adults when the vaccine antigens
closely match the circulating influenza virus strains. Because of
the decreased immunologic response among the elderly, the vaccine
is less effective in preventing the occurrence of ILI in nursing
home residents (i.e., 30%-40% effective) (4). However, vaccination
of nursing home residents is associated with a substantial (i.e.,
50%-60% effectiveness) reduction in the occurrence of serious
complications and hospitalization and with preventing death (up to
80% effective); in addition, vaccination reduces the risk for
outbreaks in nursing home settings (4,5). Antiviral agents are
recommended as an adjunct to vaccination in controlling influenza
type A. To control influenza A outbreaks in the nursing home
setting, antiviral drugs should be administered to all residents,
regardless of influenza vaccination status.

Influenza outbreak-control measures used in the New York
nursing home (e.g., rapid influenza A antigen detection and prompt
initiation of antiviral treatment and prophylaxis to all residents)
were based on recommendations of the Advisory Committee on
Immunization Practices (ACIP) (3,6) and CDC and are actively
promoted by NYSDOH. Although annual influenza vaccination of
nursing home residents is considered a standard of care, use of
antiviral agents as an adjunct to vaccination is less common,
reflecting, in part, concern about side effects and, until
recently, the protracted time required for laboratory confirmation
of influenza type A.

The use of amantadine as an adjunct for the control of
influenza type A outbreaks in New York during the current season
illustrates the usefulness of education about and promotion of the
use of antiviral agents and rapid influenza diagnostic methods. In
September 1994, NYSDOH mailed information to all health-care
facilities in New York urging health-care providers to administer
vaccine in accordance with the recommendations of the ACIP, to use
rapid antigen-detection testing and viral culture when
institutional outbreaks of ILI are initially recognized, and to use
amantadine when appropriate. On December 20, the NYSDOH sent an
electronic mail message to these institutions to report the rapid
identification of influenza type A in the first nursing home
outbreak and to reinforce the recommendations for influenza control
measures in health-care facilities.

Recommendations of the ACIP for use of amantadine and
rimantadine, the two antiviral drugs currently available for
treatment and prophylaxis of influenza type A, were published in
MMWR on December 30, 1994 (4). These recommendations also provide
information for assisting health-care providers in selecting the
appropriate drug for specific patient groups but do not recommend
preferential use of either drug.

As influenza activity continues to increase in the United
States, health-care providers should be informed about findings of
local, state, and national influenza surveillance and be familiar
with methods for rapid viral diagnosis. Updated information about
national influenza surveillance is available through the CDC
Information System by voice or fax (404) 332-4551. In addition,
providers should develop contingency plans to control influenza
outbreaks that include the use of rapid diagnosis. When possible,
policy decisions regarding use of amantadine and rimantadine should
be made before outbreaks occur.

ACIP. Prevention and control of influenza: part I, vaccines --
recommendations of the Advisory Committee on Immunization Practices
(ACIP). MMWR 1994;43(no. RR-9).

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